What defines failure to thrive (FTT) in children?

Failure to thrive (FTT) in children is primarily characterized by a consistent pattern of inadequate growth and a significant deficiency in weight gain relative to age and growth expectations. The most defining characteristic is persistent weight that falls below the 5th percentile for age. This measurement indicates a serious issue in the child's nutritional status and overall health.

When a child's weight is below the 5th percentile, it suggests that they are significantly underweight compared to their peers, raising concerns about their nutritional intake, metabolic disorders, or possible underlying health conditions. FTT is typically identified over a period of time and is not merely a single low measurement; the persistence of this low weight is crucial for diagnosis.

Other measurements, such as height or rapid weight gain, do not directly define FTT. For instance, weight below the 25th percentile and height below the 10th percentile can be indicators of growth issues but do not establish the same critical threshold as weight below the 5th percentile. Rapid weight gain can also be misleading; while it might suggest an initial improvement, it does not address the fundamental issue of sustained growth failure. Thus, the consistent and significant weight deficit depicted in the correct answer is essential for diagnosing failure to thrive.